The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Uninterruptible power supplies (UPSs) are used in supplying power to data centers. An electric utility substation downconverts utility power to generate substation power that is supplied to the UPSs, which condition the substation power. The UPSs provide back-up power to the data centers in the event of interruption of power from an electric utility and/or substation. Each of the UPSs may have a source of backup power. The UPSs may supply power to, for example, one or more power supplies of one or more servers of the data center.
A data center may have multiple loads (e.g., servers). Each of the loads has a power supply (load power supply) that may operate over a range of input voltages. One or more UPSs may be used to provide output voltage(s) to the load power supplies of the data center. The UPSs receive power from a substation at a substation voltage (e.g., 208 VAC) and may each be configured to provide output power at a fixed nominal output voltage. The UPSs may have an UPS (or inverter) mode and a bypass mode. When in the UPS mode, the UPSs may regulate, filter and condition a substation voltage to provide the output power.
Each of the UPSs may include a bypass switch that, when in the bypass mode, is in a bypass state (e.g., closed). The power from the utility at the substation voltage is provided directly to the load power supplies when the UPS is in the bypass mode without regulating, filtering and/or conditioning the substation voltage. During the bypass mode, the rectifier and inverter of the UPS may be powered down. The UPS may be in the bypass mode when, for example, a failure occurs in the UPS or the input power from the utility is clean enough that conditioning is not required. In the bypass mode, components (e.g., transformers, rectifier(s), inverter(s), etc.) of the UPS are bypassed to provide the power from the utility at the substation voltage directly to the output of the UPS and thus directly to the load power supplies.
An UPS can include a utility source input, a rectifier, an inverter, a bypass circuit and an output. Utility power is provided to the utility source input. When in the UPS mode, the power is conditioned via the rectifier and inverter prior to being provided to the output. When in the bypass mode, the power is directly provided to the output via the bypass circuit.
In addition to operating in an UPS mode and a bypass mode, an UPS may also operate in an economy mode. Different economy modes may be implemented. During a first example economy mode, the bypass switch is closed and output power of an UPS is provided via the bypass switch to a load. An inverter and/or a control module of the UPS are ON and monitor the output power of the UPS. In the economy mode, less power is consumed by the UPS than when operating in the UPS mode. This is because a rectifier of the UPS and the inverter are operating in an idle mode. While in the idle mode, the inverter is not providing power or is providing minimal power to an output of the UPS. The inverter and/or control module may switch from operating in the economy mode to the UPS mode based on the monitored output power. If the output power is noisy and/or a corresponding voltage of the output power is outside a predetermined range, the inverter and/or control module may switch from the economy mode to the UPS mode.
During a second example economy mode, the bypass switch is closed and output power of an UPS is provided via the bypass switch to a load. An inverter and/or control module of the UPS monitors the output power. Based on the output power, the inverter may supply a portion of the power supplied to the load to cancel harmonics in the power supplied via the bypass switch. The power supplied via the inverter includes harmonics to cancel the harmonics in the power supplied via the bypass switch. Although the inverter consumes more power than when operating in an idle mode, the inverter cleans the output power of the UPS while consuming less power than when operating in the UPS mode.